ext4: remove unnecessary check to avoid repeat update_backups for the same gdb

The sbi->s_group_desc contains array of bh's for block group descriptors
and continuous EXT4_DESC_PER_BLOCK(sb) bg descriptors in single block
share the same bh.
Simply call update_backups for each gdb_bh in sbi->s_group_desc will not
update same group descriptors block for multiple times.

Commit 0acdb887

 ("ext4: don't call update_backups() multiple times for
the same bg") wrongly assumed each block group descriptor in the same block
has a individual bh and unnecessary check was added.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Link: https://lore.kernel.org/r/20230826174712.4059355-13-shikemeng@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>